[matheist]

I built a userChrome.js replacement [+] back when FF 57 came around, that uses an XBL loophole to permit users to add custom javascript to their profiles that would run in the browser context. I wanted to be able to use pre-OS X Lion fullscreen mode, and couldn't find any other way to do it.

I'm a little bummed that this loophole is going away in FF 72 (I still can't get pre-Lion fullscreen!). On the other hand, it has always been super clear that this is a loophole that will eventually go away, and I did get 2 years of use out of it, so I'm not complaining too loudly. Congrats to the team for removing XBL!

[+] https://github.com/nuchi/firefox-quantum-userchromejs

[girvo]

It’s been so long that I genuinely can’t remember what that full screen mode looked like! Do you have a screenshot by any chance?

[matheist]

The content stretches all the way to the top of the screen. No menu bar, no tab bar, no toolbars.

[abyssin]

This is the only feature I miss from Chrome on OSX.